package com.idanchuang.component.config.apollo.util;

import org.springframework.beans.factory.DisposableBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.annotation.Lazy;

/**
 * 以静态变量保存Spring ApplicationContext, 可在任何代码任何地方任何时候中取出ApplicaitonContext.
 * 
 * @since version1.0
 */
@Lazy(false)
public class SpringContextUtil implements ApplicationContextAware, DisposableBean {
    
    private static ApplicationContext applicationContext = null;
    
    /**
     * 实现ApplicationContextAware接口, 注入Context到静态变量中.
     */
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) {
        SpringContextUtil.applicationContext = applicationContext;
    }
    
    /**
     * 实现DisposableBean接口,在Context关闭时清理静态变量.
     */
    @Override
    public void destroy()
        throws Exception {
        SpringContextUtil.clear();
    }
    
    /**
     * 取得存储在静态变量中的ApplicationContext.
     */
    public static ApplicationContext getApplicationContext() {
        assertContextInjected();
        return applicationContext;
    }
    
    /**
     * 从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型.
     */
    @SuppressWarnings("unchecked")
    public static <T> T getBean(String name) {
        assertContextInjected();
        return (T)applicationContext.getBean(name);
    }
    
    
    /**
     * 从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型.
     */
    public static <T> T getBean(Class<T> requiredType) {
        assertContextInjected();
        return applicationContext.getBean(requiredType);
    }
    
    /**
     * 清除SpringContextHolder中的ApplicationContext为Null.
     */
    public static void clear() {
        applicationContext = null;
    }
    
    /**
     * 检查ApplicationContext不为空.
     */
    private static void assertContextInjected() {
        if (applicationContext == null) {
            throw new IllegalStateException("applicationContext未注入,请在applicationContext.xml中定义SpringContextHolder");
        }
    }
}
